The invention relates to a method of manufacturing a semiconductor device, and more particularly, to a method of manufacturing a semiconductor device having nano wires arranged at a regular distance.
A nano wire has a diameter on the order of a nanometer (10−9 meters). Alternatively, nano wires have a lateral size constrained to tens of nanometers or less, and an unconstrained longitudinal size. At these scales, quantum mechanical effects are important, hence such wires are also known as “quantum wires.” Typical nano wires exhibit aspect ratios (length-to-width ratio) of 1000 or more. As such they are often referred to as 1-dimensional materials. Recently, it has been suggested that nano wire technology can be applied to the manufacture a highly-integrated semiconductor device.
The above-described nano wires have many interesting electronic, chemical, physical, and optical properties that are not seen in bulk or traditional 3-D materials. This is because electrons in nano wires are quantum confined laterally, and thus occupy energy levels that are different from the traditional continuum of energy levels or bands found in bulk materials. These particular properties of the nano wires can be useful for increasing the integration of a semiconductor device.
Various methods for fabricating a nano wire, such as chemical polymerization, electrochemical polymerization, chemical vapor deposition (CVD), carbothermal reduction, and the like have been suggested. Chemical polymerization is generally used because chemical polymerization can be applied to the mass production of the semiconductor device. It is easy to transform a high molecular weight nano wire formed by chemical polymerization into not only a thin film dissolved by a solvent, but also a disc-shaped film vulcanized by a spin casting process. Furthermore, electronic properties of the high molecular weight nano wire can be adjusted by a dopant doping process.
Electrochemical polymerization is used for forming a thin film on a target layer. In an electrochemical polymerization process, a predetermined current is supplied to a plurality of monomers in an electrolyte to generate a radical and a high molecular weight material, such that the radical coats an exposed layer or a wafer as a thin film. Chemical polymerization and electrochemical polymerization have been continuously studied to determine which method is more effective for formation of a thin film.
CVD is a chemical process used to produce high-purity and high-performance solid materials. In a typical CVD process, the substrate is exposed to one or more volatile precursors, which react and/or decompose on the substrate surface to produce the desired deposit. CVD is often used in the semiconductor industry to produce thin films. Particularly, the fabrication process of the semiconductor device widely uses CVD to deposit materials in various micro forms, such as monocrystalline, polycrystalline, amorphous, and epitaxial forms.
Although nano wires can be formed on the same plane through the above-described methods, a metal catalytic layer is required when nano wires are to be formed vertically over a semiconductor substrate. For instance, in order to form vertically formed nano wires, the metal catalytic layer is first deposited on the semiconductor substrate, and then CVD is performed to deposit silicon in an epitaxial form. However, it is difficult to vertically arrange formed nano wires used as a fine pattern in the semiconductor substrate at a regular distance, and to reduce a resistance of the junction between each nano wire and a wire or a line coupled to the lower portion of each nano wire.